Communication can be defined as transmission, reception and reconstruction of a transmitted signal.
Some Terms
Channel: It is the medium/space through which the information signal is transmitted. It is not completely under the control of the person designing the system.
Noise/Disturbance: It is error or undesired random disturbance of a useful information signal. This could be due to environmental disturbances or overlapping with other unwanted signals.
Modulation: It is the process of varying a property of a carrier signal, with the original signal (modulating signal) containing information to be transmitted.
Amplification: Increasing the power of the signal.
Communication System Models
Transmitter side The source sends out information which is modulated, amplified and sent across the channel through an antenna.
Receiver side The receiver receives the signal through the channel which is then demodulated and decoded to estimate the signal.
NOTE:
In ideal situations there is no noise that gets added to the transmitted signal. But in real life, there exists some noise in the received signals. So, a mathematical model which takes the noise into account to interpret the information from the signal is needed.
To decrease the error in the received signal we can send the signal repeatedly for a long time which is also called channel coding. This will be decoded on the receiving side to estimate the information in the signal.
User requirements from a communication system
Low probability of error.
Fast reception/high rate communication.
High Range communication-captured in the channel itself.
Latency - Time delay between transmission and loading is very small.
Types of Communication Models
Point-to-Point In point-to-point system, a signal is transmitted between two points of communication through a channel.
One source, multiple receivers or Broadcast Examples : radio broadcast, wireless cellular down-link. It has the following sub-types:
The transmitter sends all receivers the same signal
The transmitter sends different signals to different receivers
Both
One receiver, multiple sources or Multiple access channel Examples : Cellular up-link
